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Will upper beaches colour pink this summer?

Oostende (2020.05.12) – Nowadays, Belgian upper beaches display a remarkable appearance of European sea rocket, a succulent pioneering plant of sandy shores. A VLIZ-INBO-survey along the entire 65-kilometer coastline reveals that one out of three beaches show a strong germination of this ‘dune-engineer’, with numbers 10 to 1000 times higher than in the reference period 2003-2019. Delayed beach works and very few visitors, due to the corona lock-down, are causing this phenomenon. Whether these seedlings – on average 1000 per kilometer – will survive and blossom pink in summer, is unsure.

Many beach visitors could see for themselves the large numbers of sea rocket seedlings on Belgian upper beaches during the past few weeks, in between the flood mark and the dune- or dike basis. This succulent annual plant is exceptionally well adapted to a life in this hostile environment. It tolerates salt and a certain degree of sand cover, and is able to germinate in not more than a flood mark, i.e. buried organic material (such as beached seaweeds). Sea rocket has fleshy leaves and pink flowers in summertime. The seeds, present in thousands in late summer, disperse via sea currents, and can only germinate after a cold shock. April is the month when germination takes place, i.e. at a temperature of the sand of 10-30°C.

During 'normal years’, beach works and thousands of tourists visiting the beach at the occasion of Eastern holidays prevent this germination to take place and to grow into adult plants. This ‘corona-spring’ 2020 however, is different, particularly on the upper beach:

One out of three beaches, scattered along the coastline and always in the immediate vicinity of a coastal municipality, showed a prominent germination of hundreds to thousands of young sea rocket plants. This is 10 to 1000 times more than during a late summer reference sampling by the Research Institute for Nature and Forest (2003-2019).

One out of three beaches there was no difference whatsoever.

One out of three showed a significant decrease in numbers compared to the reference period. In most cases there was lack of space for germination, due to either beach elevation works, or to upper beaches having limited space. In the latter case, winter storms had eroded the beach up to the dune foot creating cliffs, lacking the flood marks essential for germination of sea rocket.

We estimate that overall, Sea rocket plants on Belgian beaches in April 2020 amount to about 1000 plants per kilometer of beach.

In conclusion: the lock-down due to corona, demonstrates how Belgian beaches would green with dune pioneering plants, without human interaction and under the condition beaches are sufficiently wide. European sea rocket (Cakile maritima) is not the only pioneering species of Belgian upper beaches. We found other species as well, such as the common saltwort (Salsola kali) and sand couch (Elytrigia juncea). Each of those pioneering plants are perfectly adapted to catch sand and initiate dune formation, a natural and free coastal defense against sea-level rise.